Monolithic multi-optical-waveguide penetrator or connector

ABSTRACT

Methods and apparatus are provided for a monolithic multi-optical-waveguide penetrator or connector. One example apparatus generally includes a plurality of large diameter optical waveguides, each having a core and a cladding, and a body having a plurality of bores with the optical waveguides disposed therein, wherein at least a portion of the cladding of each of the optical waveguides is fused with the body, such that the apparatus is a monolithic structure. Such an apparatus provides for a cost- and space-efficient technique for feedthrough of multiple optical waveguides. Also, the body may have a large outer diameter which can be shaped into features of interest, such as connection alignment or feedthrough sealing features.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/774,749, filed Feb. 22, 2013 and entitled “MonolithicMulti-Optical-Waveguide Penetrator or Connector,” which is hereinincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

Embodiments of the present invention relate to feedthroughs andconnectors for optical waveguides and, more particularly, to monolithicmulti-optical-waveguide feedthroughs and connectors.

Description of the Related Art

In many industries and applications, there is a need to have electricalwires or optical waveguides penetrate a wall, bulkhead, or otherfeedthrough member wherein a relatively high fluid differential pressureexists across the feedthrough member. In addition, one or both sides ofthe feedthrough member may be subjected to relatively high temperaturesand other harsh environmental conditions, such as corrosive or volatilegas, liquids, and other materials.

Recently, with the introduction of optical sensors, particularly sensorsfor use in oil and gas exploration and production and for deployment inharsh industrial environments, a need has emerged for a bulkheadfeedthrough that can seal an optical fiber at high pressures of 20,000psi and above, and high temperatures of at least 150° C. to 300° C.,with a service life of at least 5 to 20 years.

There are several problems associated with constructing such an opticalfiber feedthrough. One of these problems is the susceptibility of theglass fiber to damage and breakage. This is due to the flexibility ofthe small diameter fiber, the brittle nature of the glass material, andthe typical presence of a significant stress concentration at the pointwhere the fiber enters and exits the feedthrough. Attempts to use asealing glass, such as that used with electrical feedthroughs, have hadproblems of this nature due to the high stress concentration at thefiber-to-sealing glass interface.

Another problem with sealing an optical fiber, as opposed to sealing aconductive metal “pin” in an electrical feedthrough, is that the fusedsilica material of which the optical fiber is made, has an extremely lowthermal expansion rate. Unlike most engineering materials—includingmetals, sealing glasses, as well as the metal pins typically used inelectrical feedthroughs—the coefficient of thermal expansion of theoptical fiber is essentially zero. This greatly increases the thermalstress problem at the glass-to-sealing material interface.

As discussed above, the harsh environments where the sensors are locatedgenerally must be isolated by sealed physical barriers from otherproximate environments through which the optical fiber communicationlink of the sensor must pass. It is important to seal the bulkheadaround the optical fiber to prevent environments adjacent to the sensorfrom contaminating the optical fiber communication link. If the opticalcommunication fiber is compromised by contamination from an adjacentharsh environment, the optical fiber and all sensors to which it isconnected are likely to become ineffective.

An exemplary sensing assembly for use in harsh environments is disclosedin U.S. Pub. No. 2007/0003206 to Dunphy et al., entitled “OpticalWaveguide Feedthrough Assembly,” which is assigned to the Assignee ofthe present application and is incorporated herein by reference in itsentirety. Dunphy discloses the optical waveguide feedthrough assembly ofFIG. 1. The assembly 100 includes a front housing 10 coupled to a backhousing 12. An optical waveguide element 14 passes through a passageway16 common to both housings 10, 12. The passageway 16 is defined by boresextending across the housings 10, 12. The optical waveguide element 14includes a glass plug 18 defining a large-diameter, cane-based, opticalwaveguide preferably having an outer diameter of about 3 millimeters(mm) or greater. The glass plug 18 can have appropriate core andcladding dimensions and ratios to provide the desired outerlarge-diameter.

First and second fiber pigtails 19, 20 extend from each end of the glassplug 18. Each of the pigtails 19, 20 includes an optical waveguide suchas an optical fiber 26 encased or embedded in a carrier 28 or largerdiameter glass structure allowing the fiber 26 to be optically coupledto the glass plug 18. Sealing of the optical waveguide element 14 withrespect to the front housing 10 occurs at and/or around the glass plug18 to enable isolation of fluid pressure in communication with a firstend 22 of the passageway 16 from fluid pressure in communication with asecond end 24 of the passageway 16. This sealing of the glass plug 18with respect to the front housing 10 provides the feedthroughcapabilities of the feedthrough assembly 100. The glass plug 18 has acone-shaped tapered surface 50 for seating against a complementarytapered seat 51 of the front housing 10. Engagement between the taperedsurface 50 and the complementary tapered seat 51 that is located alongthe passageway 16 forms a seal that seals off fluid communicationthrough the passageway 16. The glass plug 18 can be machined to providethe cone-shaped tapered surface 50. Additionally, the glass plug 18 ispreferably biased against the tapered seat 51 using a mechanicalpreload.

A recess 30 formed in one end of the front housing 10 aligns with acorresponding recess 31 in one end of the back housing 12 where thehousings 10, 12 are coupled together. Preferably, the front housing 10is welded to the back housing 12 along mated features thereof. Thehousings 10, 12 preferably enclose the glass plug 18, a biasing membersuch as a first stack of Belleville washers 34, and a plunger 32, whichare all disposed within the recesses 30, 31.

The first stack of Belleville washers 34 supply the mechanical preloadby pressing the plunger 32 onto an opposite end of the glass plug 18from the tapered surface 50. Since the plunger 32 is moveable with theglass plug 18, this pressing of the plunger 32 develops a force to biasthe glass plug 18 onto the tapered seat 51 of the front housing 10located along the passageway 16 that passes through the front housing10. Transfer of force from the plunger 32 to the glass plug 18 can occurdirectly via an interface 54 between the two, which can include matingconical surfaces. The first stack of Belleville washers 34 compressesbetween a base shoulder 44 of the recess 31 in the back housing 12 andan outward shoulder 46 of the plunger 32 upon make-up of the fronthousing 10 to the back housing 12. Once the back housing 12 is welded orotherwise attached to the front housing 10 in order to keep the frontand back housings 10, 12 connected, the first stack of Bellevillewashers 34 maintains the compression that supplies force acting againstthe plunger 32.

The feedthrough assembly 100 further includes a gasket member 52disposed between the tapered seat 51 and the tapered surface 50 of theglass plug 18. The gasket member 52 comprises an annular gasket. Thegasket member 52 may be a gold foil that is shaped to complement thetapered surface 50 and the tapered seat 51. The gasket member 52 deformssufficiently to accommodate imperfections on the tapered surface 50and/or the tapered seat 51, thereby completing the seal and reducingstress between contacting surfaces due to any imperfections on thesurfaces.

The housings 10, 12 additionally enclose a cup-shaped backstop sleeve36, a second stack of Belleville washers 38, a perforated washer 40, anda centering element 42 that are all disposed within the recesses 30, 31.An outward shoulder 56 of the backstop sleeve 36 is trapped by the endof the front housing 10 and an inward shoulder 57 along the recess 31 inthe back housing 12. Contact upon sandwiching of the shoulder 56 of thebackstop sleeve 36 provides the point at which the housings 10, 12 arefully mated and can be secured together. Clearance is provided such thatthe end of the back housing 12 does not bottom out prior to the housings10, 12 being fully mated.

The centering element 42 includes an elastomeric sealing componentdisposed between the glass plug 18 and the front housing 10 that can actas a back-up seal in addition to facilitating alignment of the glassplug 18 with respect to the seat 51. The pressure in the recesses 30, 31entering from the second end 24 of the passageway 16 is higher than thepressure entering from the first end 22 of the passageway 16. Thispressure differential advantageously causes the centering element 42 todeform and press against the wall of the recess 30 and the wall of theglass plug 18, thereby creating a pressure-energized seal. One or moreholes or annular channels 43 can be formed on the outer surface of thehigh pressure side of the centering element 42. These holes or channels43 facilitate the deformation of the centering element 42 and theformation of the seal between the centering element 42 and the walls ofthe recess 30 and the glass plug 18. Additionally, the perforated washer40 enables pressurized fluid to fill the centering element 42 forproviding the energized seal.

Preferably, force transferred through the perforated washer 40 biasesthe centering element 42 into the recess 30. The second stack ofBelleville washers 38 pressed by the backstop sleeve 36 supplies thepreloading force to the perforated washer 40. The second stack ofBelleville washers 38 allow a maximum pressure force to act on thecentering element 42 such that pressure of the centering element 42against the wall of the glass plug 18 does not override force being puton the glass plug 18 to press the tapered surface 50 against the seat51.

The assembly 100 is suited for feedthrough of a single opticalwaveguide. If feedthrough of multiple waveguides is desired, a separateassembly may be used for each individual waveguide. This meansadditional costs and additional space requirements on a production tree,for example.

Accordingly, there is a need for an optical waveguide feedthroughassembly capable of operating in relatively high temperature and highpressure environments in which multiple optical waveguides are fedthrough.

SUMMARY OF THE INVENTION

Embodiments of the present invention generally relate to monolithicfeedthroughs and connectors supporting multiple optical waveguides.Certain advantages (e.g., reduced strain) provided by these monolithicstructures may also be applicable to a single (large diameter) opticalwaveguide fused into a larger capillary.

One embodiment of the present invention provides an apparatus fortransmitting light along multiple pathways. The apparatus generallyincludes a plurality of large diameter optical waveguides, each having acore and a cladding, wherein the apparatus is a monolithic structure.For some embodiments, the apparatus further includes a body having aplurality of bores with the optical waveguides disposed therein, whereinat least part of the cladding of each of the optical waveguides is fusedwith the body to form the monolithic structure.

Another embodiment of the present invention is a method for forming anapparatus for transmitting light along multiple pathways. The methodgenerally includes positioning a plurality of large diameter opticalwaveguides, each having a core and a cladding, in a plurality of boresof a body and fusing at least a portion of the cladding of each of theoptical waveguides with the body, such that the apparatus resultingtherefrom is a monolithic structure.

Yet another embodiment of the present invention provides an opticalwaveguide feedthrough assembly. The assembly generally includes ahousing, an apparatus for transmitting light along multiple pathways,wherein the apparatus is at least partially disposed in the housing, andone or more annular sealing elements disposed between an inner surfaceof the housing and an outer surface of the apparatus. The apparatus is amonolithic structure and generally includes a plurality of largediameter optical waveguides, each having a core and a cladding. For someembodiments, the apparatus further includes a body having a plurality ofbores with the optical waveguides disposed therein, wherein at least aportion of the cladding of each of the optical waveguides is fused withthe body to form the monolithic structure.

Yet another embodiment of the present invention is a method for formingan apparatus for transmitting light along multiple pathways. The methodgenerally includes positioning a plurality of large diameter opticalwaveguides, each having a core and a cladding, adjacent one another andfusing at least a portion of the cladding of each of the opticalwaveguides with the cladding of another one of the optical waveguides,such that the apparatus resulting therefrom is a monolithic structure.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 illustrates a cross-sectional view of a prior art opticalwaveguide feedthrough assembly.

FIG. 2 is a diagram conceptually illustrating a monolithicmulti-waveguide structure, according to an embodiment of the presentinvention.

FIG. 3 is a diagram conceptually illustrating a monolithicmulti-waveguide structure with a collapsed region and a larger outerdiameter region, according to an embodiment of the present invention.

FIG. 4 is a diagram conceptually illustrating a monolithicmulti-waveguide structure disposed in a housing with annulus sealsdisposed therebetween, according to an embodiment of the presentinvention.

FIG. 5 is a diagram conceptually illustrating two monolithicmulti-waveguide connectors with locating features, according to anembodiment of the present invention.

FIG. 6 is a diagram conceptually illustrating splicing of optical fibersto a monolithic multi-waveguide structure, according to an embodiment ofthe present invention.

FIGS. 7 and 8 are flow diagrams illustrating example operations forforming a monolithic structure for transmitting light along multiplepathways.

DETAILED DESCRIPTION

As described above, current approaches to optical waveguide feedthroughsuse glass to metal seals constructed from drawn cane. These approachesare limited to around 5 mm outer diameters without specialized equipmentand thus are not capable of spreading out stress loads. The approachesare non-monolithic or limited to single waveguides, thus involvingmultiple duplicates to accommodate multiple waveguides. Similarly, thecomponents are limited to single waveguide connections, or connectionsbuilt up from single waveguide approaches.

Accordingly, what is needed are techniques and apparatus to reduce glassstress when sealing multiple fiber optic components against highpressure and to achieve high temperature multi-waveguide fiber opticcable fluid block and connectorization with low loss.

Embodiments of the present invention provide techniques and apparatusfor a robust, reliable, high pressure optical waveguide feedthrough(penetrator) or connector that utilizes a monolithic glass structure. Inone embodiment, the apparatus includes a plurality of large diameteroptical waveguides, each having a core and a cladding, and a body havinga plurality of bores with the optical waveguides disposed therein,wherein at least part of the cladding of each of the optical waveguidesis fused with the body, such that the apparatus is a monolithicstructure. In another embodiment, the apparatus includes a plurality oflarge diameter optical waveguides, each having a core and a cladding,wherein at least part of the cladding of each of the optical waveguidesis fused with the cladding of another one of the optical waveguides,such that the apparatus is a monolithic structure.

Although the reduced stress and other benefits provided by suchmonolithic structures are also applicable to a single (large diameter)optical waveguide fused into a larger capillary, only monolithicstructures supporting multiple optical waveguides are described indetail below. From this description, the ideas disclosed herein can beadapted to a capillary tube having only a single bore for supporting oneoptical waveguide.

As used herein, “optical fiber,” “glass plug,” and the more general term“optical waveguide” refer to any of a number of different devices thatare currently known or may later become known for transmitting opticalsignals along a desired pathway. For example, each of these terms canrefer to single mode, multi-mode, birefringent,polarization-maintaining, polarizing, multi-core or multi-claddingoptical waveguides, or flat or planar waveguides. The optical waveguidesmay be made of any glass (e.g., silica, phosphate glass, or otherglasses), of glass and plastic, or solely of plastic. For hightemperature applications, optical waveguides composed of a glassmaterial are desirable. Furthermore, any of the optical waveguides canbe partially or completely coated with a gettering agent and/or ablocking agent (such as gold) to provide a hydrogen barrier thatprotects the waveguide.

An Example Monolithic Multi-Optical-Waveguide Penetrator

FIG. 2 conceptually illustrates a monolithic structure 200 with multipleoptical waveguides fused with multiple bores of a capillary tube 202.Embodiments of the present invention, such as the monolithic structure200, may be used in place of the optical waveguide element 14 of FIG. 1.As shown, the monolithic structure 200 includes a capillary tube 202 anda plurality of large-diameter optical waveguides 204, each waveguidehaving a core and a cladding. Before fusing, the capillary tube 202 hada plurality of bores running through the length of the capillary tube202. Although four bores are shown in FIG. 2 as an example, the tube 202may include more or less than four bores, which may depend on the numberof optical waveguides desired for a particular application. Theplurality of optical waveguides 204 are inserted into the bores. As usedherein, a large-diameter optical waveguide (also known as a canewaveguide) generally refers to an optical waveguide having an outerdiameter (of the cladding) which is greater than or equal to 1 mm (andpreferably at least 3 mm). The capillary tube 202 has a larger outerdiameter than the outer diameter of the large-diameter opticalwaveguides 204.

After insertion of the waveguide 204, the capillary tube 202 issubjected to heat in one or more selected regions to fuse the capillarytube 202 and the optical waveguides 204 (at least within the collapsedregion(s)). Typically performed with vacuum assist, this fusingcollapses the bores of the capillary tube 202 around the cladding of theoptical waveguides 204 to form a single monolithic structure. Themonolithic structure 200 is able to conduct light energy throughmultiple paths and effectively increases the outer diameter of theplurality of optical waveguides 204.

In some embodiments, the capillary tube 202 and/or the core and claddingof each optical waveguide 204 are composed of silica glass, such asquartz. In some embodiments, the optical waveguides 204 may be 1 mmquartz cane waveguides for 1550 nm light. For some embodiments, thecladding of each optical waveguide 204 and capillary tube 202 have aboutthe same temperature coefficient.

The capillary tube 202 may be a cylinder or have any of various othersuitable shapes. The capillary tube 202 may be made of quartz formed bydrawing or drilling (e.g., multibore tubing offered by Friedrich &Dimmock, Inc. of Milleville, N.J.). The capillary tube 202 may be shapedby grinding, machining, or other means to form any feature of interest.

According to one embodiment, the capillary tube 202 may be shaped toform geometries important to sealing and stress reduction. For example,FIG. 3 illustrates another monolithic structure 300, similar to themonolithic structure 200 of FIG. 2, where the capillary tube 202includes a collapsed region 306 (wherein fusing of the bores and opticalwaveguides 204 has occurred) and a shaped sealing region 308. In theembodiment shown in FIG. 3, the sealing region 308 has a convexfrustoconical shape. The tapered ends of the convex frustoconical shapedsealing region 308 form sealing surfaces that are large compared to theouter diameter of the optical waveguides 204 and the collapsed region306. In this manner, when the monolithic structure 300 is disposed in awellhead feedthrough assembly, for example, downhole pressure may bedistributed on the monolithic structure 300 in a desired manner, with asurface reacting force acting on the sealing surface furthest away fromthe collapsed region.

In some embodiments, as shown in FIG. 4, the monolithic structure 200may further include one or more annulus seals 410 (e.g., Accuseal,offered by Weatherford International with headquarters in Houston, Tex.)around the capillary tube 202 in collapsed region 306. The annulus seals410 may be any of various suitable sealing elements, such as v-ringseals, chevron seals, o-ring seals, gasket seals, etc. The annulus seals410 see internal pressure within a metal housing 412 corresponding tothe outer diameter of the annulus seals 410. The glass, however, seesinternal pressure within the metal housing corresponding to the smallerouter diameter of the capillary tube 202 in the collapsed region 306.According to some embodiments the annulus seals 410 seal an annulusaround the smaller diameter collapsed region 306, while sealing region308 has a larger outer diameter and thus reacts to the axial force onthe optical waveguide 204 over a much larger area (surface reactingforce) which provides reduced stress on the glass.

An Example Monolithic Multi-Optical-Waveguide Connector

In some embodiments, the capillary tube 202 may be shaped to formgeometries important to alignment of two monolithicmulti-optical-waveguide connectors. As shown in FIG. 5, the capillarytube 202 may be shaped to include at least one locating feature 514. Inthe embodiment shown in FIG. 5, the locating feature 514 is a flat(i.e., a flat surface) along a length of the capillary tube 202. Theflat is formed in an outer diameter of the capillary tube 202 and isparallel to an axis of the capillary tube 202. The capillary tube 202may be divided (e.g., by cutting or dicing) in the collapsed region 306to form a connector pair. The locating feature 514 allows the opticalwaveguides 204 to be realigned within the desired submicron alignment.In one embodiment, the parted capillary tube 202 may be realigned bybutting the diced ends 512 against one another and using the flat(locating feature 514) to precisely align the outer diameter, therebyalso aligning the optical waveguides 204. This is particularly usefulfor undersea wet connects. In some embodiments, the ends 512 of the cutportion may have a polished face. In some embodiments, rather thanhaving flat faces, the diced ends 512 may be aligned and connected usingmale/female connectors, where each end 512 is shaped to mate with theother end 512.

As shown in FIG. 6, in some embodiments, individual optical waveguides204 may be spliced using a cone or carrier splice at 616, for example,with optical fibers 618. In carrier splicing, for example, all but oneof the carriers (which may be the optical waveguides 204) are pulledback, the remaining carrier is spliced, and this process is repeated foreach carrier. In another embodiment, the carriers may be spliced usinglarge diameter splicing (LDS) to the ends of the cane waveguides.

Example Methods for Making a Monolithic Multi-Optical-WaveguidePenetrator or Connector

FIG. 7 is a flow diagram illustrating example operations 700 for formingan apparatus for transmitting light along multiple pathways. Theoperations 700 begin, at 702, by positioning a plurality of largediameter optical waveguides (e.g., waveguides 204), each having a coreand a cladding, in a plurality of bores of a body (e.g., the cylindricalcapillary tube 202 of FIG. 2). According to some embodiments, the boresmay be drilled in the body prior to positioning the optical waveguidesin the bores. For other embodiments, the body having the plurality ofbores may be drawn from a preform having a plurality of bores.

At 704, at least a portion of the cladding of each of the opticalwaveguides is fused with the body, such that the apparatus resultingtherefrom is a monolithic structure (e.g., structure 200). For someembodiments, at least one orientation feature may be formed in the bodybefore the fusing at 704 or in the apparatus after the fusing.

At 706, the apparatus may be diced in the fused portion to form twoapparatuses. Each of the two apparatuses may be a monolithic structure(e.g., if the dicing occurs in the collapsed region 306). For someembodiments, an end face of at least one of the two apparatuses may bepolished at 707. For some embodiments, at least one orientation featuremay be formed in the two apparatuses (e.g., in the end faces 512 of thetwo apparatuses).

At 708, the end faces of the two apparatuses may be butted together,such that the optical waveguides in the two apparatuses are aligned. Theoptical waveguides may be aligned using at least one orientation feature(e.g., locating feature 514) in at least one of the two apparatuses. Insome embodiments, the orientation feature may be at least one flatsurface formed in an outer diameter of the body and parallel to an axisof the body.

At 710, a plurality of optical fibers (e.g., fibers 618) may be spliced(e.g., at 616) to the plurality of large diameter optical waveguides.The splicing may involve cone splicing or carrier splicing.

For some embodiments, a monolithic structure as described above may beformed without using a body (e.g., a capillary tube). For example, FIG.8 is a flow diagram illustrating example operations 800 for forming anapparatus for transmitting light along multiple pathways by fusing thecladdings of multiple large diameter optical waveguides together. Theoperations 800 may begin, at 802, by positioning a plurality of largediameter optical waveguides (e.g., waveguides 204), each having a coreand a cladding, adjacent one another (e.g., in a bundle).

At 804, at least a portion of the cladding of each of the opticalwaveguides is fused with the cladding of another one of the opticalwaveguides, such that the apparatus resulting therefrom is a monolithicstructure. This fusing may be performed in the same region on each ofthe optical waveguides, such that the monolithic structure may be usedas an optical feedthrough.

Many of the operations 700 of FIG. 7 described above may also beperformed for the monolithic structure formed according to theoperations 800 of FIG. 8. For example, the apparatus may be diced in thefused portion to form two apparatuses, which may be polished and laterbutted together (e.g., using one or more orientation features foralignment).

Embodiments of the invention heretofore can be used and have specificutility in applications within the oil and gas industry. Further, it iswithin the scope of the invention that other commercial embodiments/usesexist with one such universal sealing arrangement shown in the figuresand adaptable for use in (by way of example and not limitation)industrial, chemical, energy, nuclear, structural, etc. While theforegoing is directed to preferred embodiments of the invention, otherand further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. An apparatus for transmitting light along multiple pathways, comprising: a plurality of large diameter optical waveguides, each having a core and a cladding, wherein the apparatus is a monolithic structure; and a body having a plurality of bores with the optical waveguides disposed therein, wherein at least part of the cladding of each of the optical waveguides is fused with the body to form the monolithic structure and wherein the body comprises at least one orientation feature.
 2. The apparatus of claim 1, wherein the at least one orientation feature comprises at least one flat surface formed in an outer diameter of the body and parallel to an axis of the body.
 3. The apparatus of claim 1, wherein the body has at least two different outer diameters.
 4. The apparatus of claim 3, wherein the body comprises a sealing surface between the at least two different outer diameters.
 5. The apparatus of claim 4, wherein the sealing surface comprises a convex frustoconical section between the at least two different outer diameters.
 6. The apparatus of claim 1, wherein a temperature coefficient of the cladding of each of the optical waveguides is about the same as a temperature coefficient of the body.
 7. The apparatus of claim 1, wherein the body and the core and cladding of each of the optical waveguides comprise silica glass.
 8. The apparatus of claim 1, wherein the body is a cylindrical capillary tube.
 9. The apparatus of claim 1, wherein an outer diameter of the cladding of the large diameter optical waveguides is at least 1 mm.
 10. An optical waveguide feedthrough assembly comprising the apparatus of claim 1, the optical waveguide feedthrough assembly further comprising: a housing, wherein the apparatus is at least partially disposed in the housing; and one or more annular sealing elements disposed between an inner surface of the housing and an outer surface of the apparatus.
 11. The assembly of claim 10, wherein the annular sealing elements comprise at least one of v-ring seals, o-ring seals, or gasket members.
 12. The assembly of claim 10, wherein the housing comprises metal and wherein the body and the core and cladding of each of the optical waveguides comprise silica glass.
 13. The assembly of claim 10, wherein the housing comprises a cylindrical tube. 